Amount Of Pre-adsorbed Water Research Articles

CO2 sorption in wet ordered mesoporous silica kit-6: effects of water content and mechanism on enhanced sorption capacity

The sorption isotherms of CO2 in wet ordered mesoporous silica KIT-6 with different amounts of pre-adsorbed water were firstly collected experimentally using a volumetric method in the temperature range of 275–281 K. The isotherms show an inflection point indicating CO2 hydrates form in the pore spaces which is proofed by the enthalpy change calculated at the inflection pressure, and the quantity of water content shows considerable effect on the sorption capacity of CO2. The highest enhancement of sorption capacity in the presence of water is observed in wet KIT-6 sample with water loadings of 2.48, which is about 12.80 mmol/g and 1.86 times than that on dry sample. However, the saturation capacity is still far less than that what can be stored merely in the form of hydrates due to the low ratio of water utilization because of the large pore and the polar surface of KIT-6.

Synthesis of hollow glass-ceramics microspheres via template method

Hollow glass-ceramics microspheres (HGCM) were successfully fabricated by a simple technique using polyacrylamide microspheres (PAM) as template. The corresponding HGCM were obtained by a thermal treatment of the core–shell microspheres, which were synthesized with organic template method. The effects of the concentration of glass powder, the Hydrophile–Lipophile Balance (HLB) value, and the amount of pre-adsorbed water on the morphologies of the core–shell microspheres and HGCM have been investigated. The size, morphology, core–shell structure and crystalline phase of HGCM and core–shell microspheres were determined via XRD, SEM and TGA. The influences of initiator and surfactant on the monodispersity and average diameter of PAM were investigated via SEM. The results showed that: (a) the average diameter and monodispersity of PAM can be controlled by varying the amount of initiator and surfactant, and (b) the agglomeration of core–shell microspheres and HGCM can be reduced using PAM with pre-adsorbed water and adjusting the HLB value. In addition, the amount of solid beads decreases obviously by reducing the concentration of glass powder and adjusting the HLB value.

Dependence of the C Constant in the Brunauer-Emmett-Teller Equation on Water Pre-Adsorbed on Activated Carbon

The dependence of the C constant in the BET equation on the amount of pre-adsorbed water has been investigated by low-temperature nitrogen adsorption on activated carbon containing different amounts of water pre-adsorbed at the same relative water vapour pressure. It is suggested that the rapid decrease in the surface area as determined by the BET method in comparison with the C value in cases of low degrees of sorption volume filling is associated with blocking of part of the carbon texture and the parallel formation of extremely narrow micropores.

The adsorption of 1,4-dioxan, tetrahydrofuran and tetrahydropyran from binary solution with methanol on Al3+ and Cr3+-exchanged montmorillonite

AbstractSurface excess isotherms were determined for the adsorption of 1,4-dioxan (DIOX), tetrahydropyran (THP) and tetrahydrofuran (THF) from binary solution with methanol (MeOH) on Al3+- and Cr3+-exchanged, montmorillonite containing different amounts of pre-adsorbed water. The isotherm type is dominated by the binary mixture whereas the amplitude, which follows the sequence DIOX > THP > THF, is further influenced by the exchange cation, Al3+ > Cr3+, and the water content of the clay. The sorption of DIOX and THP from MeOH exhibit a type IV isotherm in the Schay-Nagy classification on both cation-exchanged forms, whilst that of THF from MeOH is of type I and THF is the preferred adsorbate. The azeotropic point for the type IV isotherms is close to a 1:1 mole ratio for the samples dried at 120°C but when the samples are rehydrated at 12% r.h. following thermal pretreatment at 120°C the azeotropic point shifts in favour of the cyclic ethers DIOX and THP, making them the preferred component over a substantial portion of the composition range.